Sorter conveyor

ABSTRACT

A sorter conveyor having cross-belts for supporting and discharging article is disclosed, wherein the cross-belts are driven by interaction between a rotor moving with the cross-belts and stationary electric stator parts, wherein the rotor is arranged separate from the cross-belt and is connected to a drive roller with a transmission. Further is disclosed such sorter conveyors having tilt-trays driven by interaction between rotors moving with the tilt-trays and stationary electric stator parts, as well as such sorter conveyors which are driven along the stationary track by means of stationary linear motor stator parts interacting with the reaction means. Lastly, rotors and the manufacture of such rotors are disclosed.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/DK02/00045 which has an Internationalfiling date of Jan. 22, 2002, which designated the United States ofAmerica and which claims priority on Danish Patent Application number DKPA 2001 00107 filed Jan. 22, 2001, the entire contents of which arehereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to sorter conveyors having cross-belts forsupporting and discharging articles, wherein the cross-belts are drivenby interaction between reaction means moving with the cross-belts andstationary electric stator parts, also known as Arch Induction Motors.

The invention further relates to sorter conveyors having tilt-trays forsupporting and discharging articles, wherein the tilting of the traysare driven by interaction between reaction means moving with thetilt-trays and stationary electric stator parts.

Furthermore, the invention relates to such sorter conveyors which aredriven along the stationary track by means of stationary linear motorstator parts interacting with the reaction means.

Lastly, the invention relates to rotors and the manufacture of rotorssuitable of being employed as said reaction means.

BACKGROUND

Sorter conveyors comprising a plurality of cross-belt units forsupporting articles and transport these along a stationary track partforming a closed loop from one or more induction stations to a pluralityof different discharge stations are well-known in the art.

A problem with respect to such sorter conveyors is that a drive unitmust be provided for each cross-belt unit to move said belt fordischarge of articles and, in case of induction of articles from theside of the sorter conveyor, also during induction of the articles.Commonly, each cross-belt unit is provided with a separate electricmotor that is expensive to provide and maintain and which requires atransfer of power to the moving part of the sorter conveyor by means ofe.g. inductive energy transfer or an electrical rail and collectorshoes. Also, a control system must be provided on the moving part of thesorter conveyor as well as means for transferring control signals tosaid control system.

A known solution is to equip the sorter with stationary electric statorparts capable of producing a pulsating electrical field where a movementof the cross-belts may be required, and to equip each cross-belt unitwith a drive part that is susceptible to said electrical field such thatthe cross-belts may be driven by means of the stationary electric statorpart, thus making the provision of complete electric motors on themoving part of the sorter conveyor redundant.

It is known from FR 2 096 810 by Jeumont-Schneider to provide eachcross-belt with a plurality of metallic strips parallel to the directionof movement of the sorter, thereby making the belt itself susceptible tothe field from the stationary electric stator parts.

A solution allowing the use of standard cross-belts is disclosed in EP 0425 021 by Van den Goor, in which a reaction roller being susceptible tothe field for the stationary electric stator part is provided on eachcross-belt unit, wherein the cross-belt is in contact with the reactionroller over part of the circumference of said roller to provide driveforce from the reaction roller to the belt by friction. The cross-beltis guided along the part of the circumference of the reaction rollerbeing opposite to the part facing the stationary electric stator part bymeans of two rollers biasing the cross-belt towards the reaction roller.

It is a problem with the latter discussed sorter conveyor that thecross-belt requires contact with as large a part of the circumference ofthe reaction roller as possible in order to provide the necessaryfriction force between the cross-belt and the reaction roller, and thestationary electric stator parts requires magnetic contact with as largea part of the circumference of the reaction roller as well in order toprovide a satisfactory degree of efficiency of the system for drivingthe cross-belt. However, the cross-belt and the two biasing rollerslimit the circumferential part of the reaction roller available to thestationary electric stator parts. Thus, both the cross-belt and thestationary electric stator parts requires access to as large a part ofthe circumference of the reaction roller as possible.

It is an object of the present invention to provide a cross-belt sorterconveyor with stationary electric stator parts for driving thecross-belts, in which the above-discussed problem of access to thecircumference of the reaction roller for both the cross-belt and thestationary electric stator parts is relieved.

One solution would be to guide the cross-belt around the reaction rollerbetween the reaction roller and the stationary electric stator parts butthis results is an increased distance or gap between the reaction rollerand the stationary electric stator parts, resulting in an increasedmagnetic reluctance and a lower efficiency of the drive system.

The solution provided with the present invention is to separate thefunction of the known reaction roller into a rotor being susceptible tothe field of the stationary electric stator parts, a drive roller whichover a part of its circumference is in driving contact with thecross-belt, and a transmission between the rotor and the drive rollerfor transmitting the drive force there between.

This solution provides other advantages as well. The two biasing rollersare made redundant and simpler bearing may be used for the rotor ascompared to the reaction roller of the prior art because the bearing isrelieved from the forces due to the internal stress of the cross-belt.

The separation of the function of the reaction roller into the rotor andthe drive roller also permit a gearing between the two by means of thetransmission, such that the circumferential speed of the rotor may bedifferent from, and in particular higher than that of the drive roller.Thereby, a given rotor may yield more power as the power is proportionalwith the circumferential speed. Furthermore, a feed-back system forproviding a measure of the movement of the cross-belt to the stationarycontrol system of the sorter conveyor by means of measuring the rotationof the rotor may be given a better resolution due to the gearing. A yetfurther advantage occur in case the cross-belt is locking means ofbraking the rotor when the units are passing curved parts of thestationary track by and a gearing is made between the rotor and thedrive cylinder, as a locking torque applied to the rotor will bemultiplied by the gearing ratio when acting on the cross-belt.

The separation of functions also allows for a more flexible design ofthe cross-belt units and facilitates that the rotor may be situated atthe level of the tracks on which the sorter moves or even lower in orderto be in close contact with the stationary electric stator parts.

Other objects and advantages of the present invention will be apparentfrom the description of the invention.

The present invention relates in a second aspect to a sorter conveyorcomprising tilt-tray units for supporting articles and transport thesealong a stationary track part forming a closed loop from one or moreinduction stations to a plurality of different discharge stations, inwhich the tilt of the trays are driven by means of electric motors whichhas turned out to be advantageous and is disclosed e.g. in WO 00/71446.It is however expensive to provide each tilt-tray unit with a separateelectric motor and to maintain or replace motors due to malfunction ofthe active parts of the motor. The motors require a transfer of power tothe moving part of the sorter conveyor by means of e.g. inductive energytransfer or an electrical rail and collector shoes. Also, a controlsystem must be provided on the moving part of the sorter conveyor aswell as means for transferring control signals to said control system.This type of sorter conveyors have been improved by the second aspect ofthe present invention by providing at least one stationary electricstator part along the stationary track part of the sorter conveyor, thestator parts being arranged to selectively produce a travelling magneticfield, and by arranging a rotor susceptible to said travelling magneticfield on each tilt-tray unit such that it may apply a driving force totilt the tray when co-operating with the at least one stationaryelectric stator part. Thus, the requirement of one electric motor andthe provision of electric power and control signals on the moving partof the sorter conveyor are made redundant.

The present invention relates in a third aspect to a sorter conveyorhaving arranged along the stationary track part at least one stationaryelectric stator part that may be activated selectively to produce atravelling magnetic field, and for each article-supporting unitcomprises a rotor susceptible to said travelling magnetic field andarranged to apply a driving force to the discharge means whenco-operating with the at least one stationary electric stator part, suchas according to the two first aspects of the present invention asdiscussed above. The sorter conveyor requires drive means for drivingthe moving part along the stationary track part, which drive means maybe stationary linear motors interacting with reaction means on themoving part, such as an aluminium plate covering a steel plate for alinear asynchronous motor drive or a set of permanent magnets for alinear synchronous motor drive. In both cases, it has been found that anadvantage may be obtained by letting one or more stationary linear motorstator parts interact with the rotors to produce a driving force todrive the sorter along the stationary track part, thus letting therotors take the place of the separate reaction means and making thesorter lighter and less expensive in construction.

The present invention relates in a fourth aspect to a simple rotor andto a method of manufacturing such rotor. A rotor for interacting with astationary electric stator in an asynchronous manner may comprise aninner steel tube covered by an outer tube of a suitable material, suchas copper or preferably aluminium, the inner surface of the aluminiumtube being in contact with the outer surface of the steel tube. Suchrotors are commonly manufactured by processing said two surfaces to amutual interference fit, e.g. by turning the tubes, where after thetubes are assembled to a rotor. The tolerances have to be small, as thelength of the aluminium tube does not allow for much pressing forcebefore giving in to buckling. This manufacturing method islabour-intensive and the rotors are therefore relatively expensive. Oneobject of the present invention is to provide less expensive rotors.

Such rotor may according to the present invention comprise one actualtube and the second of the inner or outer tubular members consist of alength of material being deformed into a tubular shape fastened to thefirst tubular member so as to preserve the tubular shape of the secondtubular member as well as the contact between the two tubular members.Thereby, the rotor may be manufactured in a less expensive manner.

BRIEF DESCRIPTION OF THE PRESENT INVENTION

The present invention relates in a primary aspect to a conveyorcomprising

-   -   a stationary track part,    -   at least one stationary electric stator part that may be        activated selectively to produce a travelling magnetic field and        is arranged along the stationary track part,    -   a sorter movably arranged to be driven along the stationary        track part by means of drive means, and    -   a plurality of article-supporting units arranged on the sorter,        each unit having    -   a flexible member defining an article-supporting surface and        being arranged movably in a direction substantially        perpendicularly to the direction of motion of the sorter, and    -   a rotor susceptible to said travelling magnetic field and        arranged to apply a driving force to the flexible member when        co-operating with the at least one stationary electric stator        part,        wherein the conveyor is distinct from the prior art in that each        article-supporting unit comprises    -   a drive roller which over a part of its circumference is in        driving contact with the flexible member, and    -   a transmission means for transmitting driving force from the        rotor to the drive roller.

The flexible member, i.e. the cross-belt, may in a preferred embodimentbe an endless belt as is commonly known from cross-belt sorters.However, flexible sheets or chain-like arrangements of a finite lengthmay also be applied within the present invention.

The rotor is required to be susceptible to the travelling magneticfield, which may be provided by irregularities of the magneticproperties along the circumference of the rotor, such as the reluctanceof the rotor, longitudinal grooves forming teeth and creating anirregularity of the magnetic conducting properties or the presence ofpermanent magnets in the rotor. However, a preferred type of rotorcomprises an inner steel tube and an outer aluminium tube togetherforming a rotor that operates as a part of an induction motor with thestationary electric stator parts.

It is preferred to use a toothed belt and two toothed wheels astransmission means, but other types as chain transmission, gear wheels,a drive shaft with bevel gear wheels etc. may likewise be employed bythe skilled person.

The transmission means may advantageously have a gearing ratio in therange of 1.5 to 5, preferably in the range of 2 to 4, between the rotorand the drive roller, so that the rotor has a higher angular speed thanthe drive roller. A gearing ratio of about 3 has been found to be verysuitable. The advantages of the gearing ratio are discussed previously.

In order to prevent the cross-belts with articles thereon to startmoving when passing curved parts of the stationary tracks due to theapparent centrifugal force, causing the articles to be dischargedunintentionally, the conveyor may comprise locking means for preventingthe motion of the flexible members of the article-supporting units.Prior art cross-belt units having a complete electric motor on unit maybe locked by means of the motor but this opportunity does not exist withthe conveyor according to the present invention. The lack of lockingmeans for the cross-belt puts a limit to the maximum conveyance speed ofa given conveyor, whereas the existence of locking means allows forhigher conveyance speeds and thereby higher efficiency of the conveyor.

The locking means may be passive means such as wheels mounted stationaryon the curved track part to engage the cross-belts and prevent them frommoving transversely to the direction of conveyance.

Active locking means are however preferred, in particular locking meansthat are activated contact-less, such as locking means that areactivated by the deviation from alignment of adjacent article-supportingunits in curved sections of the stationary track part. The pinching ofthe consecutive article-supporting units on the inside of the curvesand/or the elongation between points on consecutive article-supportingunits on the outer side of the curves provides a suitable drive meansfor activating locking means. Alternatively, the apparent centrifugalforce on article-supporting units moving in curved sections of thestationary track part may be used as drive means for driving theactivation of the locking means, e.g. by means of a spring affected massbeing movable transversely to the conveyance direction and activatingthe locking means under influence of the apparent centrifugal force.

According to other embodiments, the locking means may be brakingconstantly and only be released when needed, e.g. being released bymeans of magnetic forces applied by stationary electromagnets, such asthe stationary electric stator part acting on a release means, such as asteel bar, or by means of the attraction forces between the at least onestationary electric stator part and the rotor. These magnetic forcesmay, depending on the layout of the system, exert a downward or upwardforce on the rotor as well as a force in or against the direction ofconveyance, which force may be employed to release the locking.

According to another embodiment having a constant locking effect, thelocking means comprises on each article-supporting unit a stationarypart in engagement with a movable part moving simultaneously with theflexible member, characterised in that the resistance against mutualmovements between the stationary part and the movable part issubstantially lowered during mutual movement between said two parts. Inparticular, the stationary part may be a support surface supporting theside of the flexible member opposite the article-supporting surface, andthe friction characteristics between the flexible member and the supportsurface are characterised in that the friction is substantially loweredat mutual movement between said two parts.

Another manner of preventing articles from being dischargedunintentionally when passing curved track sections is to provide tiltingmeans for tilting the article-supporting surfaces inwardly when passingcurved sections of the stationary track part, and drive means fordriving said tilting means, wherein said drive means are driven by thedeviation from alignment of adjacent article-supporting units in curvedsections of the stationary track part.

As no active control means are present on the moving part of theconveyor in preferred embodiments, the conveyor should comprise feedbackmeans for providing a output to a control unit of the conveyorindicative of the movement of the flexible member, so that the movementmay be measured and thereby the function of the flexible member.

One method of providing a feedback is where the feedback means comprisea camera for detecting at least two consecutive images of at least oneof the flexible member, the rotor or the transmission, and computingmeans for providing an output from said images.

It is preferred that the feedback means detect the extend of rotation ofthe rotor of each of the article-supporting units and provide an outputaccordingly. This may be realised if the rotor comprises at least oneirregularity of the susceptibility to the travelling magnetic filed,causing the power supplied to the stationary electric stator to varywhen the at least one irregularity passes the stationary electric statorduring rotation of the rotor, said variation being detected by thefeed-back means. Another manner of realising the feedback is when theouter surface of the rotor comprises at least one irregularity of itsoptical characteristics, such as a colour variation or a reflectivityvariation, and the feedback means comprises a detector for detecting thevariation of reflection of a light source caused by the at least oneirregularity during rotation of the rotor and providing an outputaccordingly. The irregularity may e.g. be in the form of linespreferably being parallel to the axis of rotation of the rotor.

Yet another embodiment includes that each article-supporting unitcomprises signal means for producing a signal indicative of the movementof the flexible member and the feed-back means comprises a detector fordetecting said signals and producing an output accordingly. The signalmay be an audio signal, e.g. from a ratchet mounted on the rotor, or avisual signal, e.g. produced by means of a piezo electric crystal thatis deformed by an eccentric wheel mounted on the rotor shaft and a pairof spark electrodes connected thereto, producing detectable sparksduring rotation of the rotor.

A yet further embodiment includes signal means that comprises at leastone passive circuit moving simultaneously with the flexible member, thepassive circuits having an induction part for inducting an electriccurrent when exposed to a magnetic field and a transmitter part fortransmitting a electromagnetic signal and driven by the inductedcurrent, the feed-back means comprising a detector for detecting saidsignal and providing an output according to the variations of the signaldue to said movement of the one or more passive circuits. This passivecircuit, known as radio frequency or RF-tags, may also be used foridentification of the individual article-supporting unit.

It is of importance for the efficiency of the interaction between therotor and the stationary electric stator parts that the air gap betweenthe two is made as small as possible. An adjustment of the position ofthe stator parts is only partly sufficient as a certain play must beallowed for variations between the article-supporting units due toinaccuracy of production and changes caused by wear. It is therefore, inorder to minimise the air gap for each article-supporting unit,preferred that the conveyor comprises horizontal alignment means forsituating the article-supporting units precisely with respect to the atleast one stationary electric stator part in the direction transverselyto the conveyance direction of the conveyor.

One means for providing horizontal alignment comprises a horizontalwheel on the article-supporting unit, which wheel engages a two-sidedtrack of the track part allowing a very small play between the wheel andthe two-sided track, thereby ensuring the correct horizontal position ofthe rotor with respect to the stationary electric stator part.

In particular, the horizontal alignment means may comprise biasing meansfor providing a biasing force to the article-supporting units toward oneside in the transversal direction and reaction means for producing acounter reaction force against said biasing force. The biasing means maybe springs or the like, or the biasing means may in a particularembodiment comprise at least one permanent magnet arranged on each ofthe article-supporting units and a magnetic susceptible stationary partarranged near the at least one stationary electric stator part displacedin the transversal direction with respect to said at least one permanentmagnet such that the mutual magnetic force between the at least onepermanent magnet and said stationary part constitutes said biasingforce.

Alternatively or additionally, the at least one stationary electricstator part may be suspended movably and comprises biasing means forbiasing the stator part towards the rotors of the article-supportingunits and one or more distance means for providing a suitable distancebetween the stator part and the rotors.

The rotors may also, as discussed previously, be used for driving thesorter, so that said drive means for driving the sorter along thestationary track part comprises one or more stationary linear motorstator parts interacting with said rotors to produce a driving force todrive the sorter along the stationary track part.

According to the second aspect of the present invention, it furtherrelates to a conveyor comprising

-   -   a stationary track part,    -   at least one stationary electric stator part that may be        activated selectively to produce a travelling magnetic field and        is arranged along the stationary track part,    -   a sorter movably arranged to be driven along the stationary        track part by means of drive means, and    -   a plurality of article-supporting units arranged on the sorter,        each unit having    -   a tray defining an article-supporting surface and being arranged        to be tilted in a direction substantially perpendicularly to the        direction of motion of the sorter, and    -   a rotor susceptible to said travelling magnetic field and        arranged to apply a driving force to tilt the tray when        cooperating with the at least one stationary electric stator        part.

The above-discussed feedback means, alignment means and drive meanscomprising stationary linear motor stator parts interacting with saidrotors may suitably be applied to the conveyor according to this secondaspect.

The present invention relates in a third aspect to a conveyor comprising

-   -   a stationary track part,    -   at least one stationary electric stator part that may be        activated selectively to produce a travelling magnetic field and        is arranged along the stationary track part,    -   a sorter movably arranged to be driven along the stationary        track part by means of drive means, and    -   a plurality of article-supporting units arranged on the sorter,        each unit having    -   article-supporting means defining an article-supporting surface        and having discharge means to discharge articles therefrom in a        direction substantially perpendicularly to the direction of        motion of the sorter, and    -   a rotor susceptible to said travelling magnetic field and        arranged to apply a driving force to the discharge means when        co-operating with the at least one stationary electric stator        part,        wherein said drive means comprises one or more stationary linear        motor stator parts interacting with said rotors to produce a        driving force to drive the sorter along the stationary track        part.

The present invention relates in a fourth aspect to a method formanufacturing a tubular rotor for an asynchronous motor comprising aninner tubular magnetic conducting member, such as a steel tube, and anouter tubular member being electric conducting and non-magneticconducting, such as aluminium or copper, the method comprising the stepsof

-   -   providing a first of said tubular members,    -   providing at least one length of material for the second of said        tubular member,    -   deforming said at least one length of material into a tubular        shape to form the second tubular member and applying the second        tubular member in contact with said first tubular member, and    -   fasten the second tubular member to the first tubular member so        as to preserve the tubular shape of the second tubular member as        well as the contact between the two tubular members.

It is preferred that the at least one length of material is resilientand is deformed into a shape so that resilient forces in the secondtubular member and counteracting reaction forces from the first tubularmember fasten the second tubular member to the first tubular member.According to one embodiment thereof, the first tubular member is theinner member and the second tubular member is formed from a sheetmaterial that is rolled to a curvature diameter less than the outerdiameter of the first tubular member prior to being applied to the outerperimeter of the first tubular member. According to a second embodimentthereof, the first tubular member is the outer member and the secondtubular member is formed from a wire, preferably of a rectangular, suchas quadratic cross-section, that is coiled to a helical shape of adiameter exceeding an inner diameter of the first tubular member, thesecond tubular member being stretched prior to being inserted into thefirst tubular member where after the stretching is released.

According to yet another embodiment, the first tubular member is theouter member and the second tubular member is formed from one or moresheets of material which each is rolled to a curvature diameterexceeding an inner diameter of the first tubular member and a perimeterlength less than the inner perimeter length of the aluminium tube, eachsheet being compressed to a diameter less than the inner diameter of thefirst tubular member prior to being inserted into the first tubularmember, where after the compression is released.

According to an alternative method, the first tubular member is theinner member and the second tubular member is formed from a sheetmaterial that is wound in a plurality of layers on the first tubularmember. The sheet material may be fastened e.g. by means of glue, bywelding or by deformation of the sheet when wounded on the first tubularmember.

The present invention relates according to the fourth aspect also to atubular rotor for an asynchronous motor comprising an inner tubularmagnetic conducting member and an outer tubular member being electricconducting and non-magnetic conducting, wherein a first of said tubularmembers is a tube and the second of said tubular members consist of alength of material being deformed into a tubular shape fastened to thefirst tubular member so as to preserve the tubular shape of the secondtubular member as well as the contact between the two tubular members.The rotor may be manufactured according to one of the above-discussedmethods.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention is for illustrative purposes shown in theattached drawings of which

FIG. 1 is an end view of a cross-belt unit according to one embodimentof the present invention,

FIG. 2 is a first perspective view of the cross-belt unit of FIG. 1,

FIG. 3 is a second perspective view of the cross-belt unit of FIG. 1,

FIG. 4 is a schematic perspective view of the embodiment of a cross-beltunit of FIGS. 1-4,

FIG. 5 is a schematic perspective view of a second embodiment of across-belt unit,

FIG. 6 is a cross-section of the cross-belt unit of FIG. 5,

FIG. 7 is a perspective view of a section of a sorter conveyor havingcross-belt units according to FIGS. 5 and 6,

FIG. 8 is a perspective view of a sorter conveyor having cross-beltunits according to FIGS. 5 and 6,

FIGS. 9 a)-d) show an embodiment of a feed-back system,

FIG. 10 is an embodiment of horizontal alignment of thearticle-supporting unit,

FIG. 11 is an embodiment of vertical alignment of the article-supportingunit,

FIGS. 12 a) and b) show an embodiment of the rotor with a helical rolledsteel tube,

FIGS. 13 a) and b) show an embodiment of the rotor with rolled shellsforming the steel tube,

FIGS. 14 a) and b) show an embodiment of the rotor with an aluminiumsheet forming the outer tube, and

FIGS. 15 a) and b) show an embodiment of the rotor with a helical woundquadratic wire forming the steel tube,

FIG. 16 is a perspective view of a tilt-tray unit according to thesecond aspect of the invention,

FIG. 17 is a cross-section of the tilt-tray unit of FIG. 16,

FIG. 18 is a perspective view of a section of a sorter conveyor havingthe tilt-tray units of FIG. 16, and

FIG. 19 is a perspective view of a sorter conveyor having the tilt-trayunits of FIG. 16.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The cross-belt unit 1 shown in FIGS. 1-3 comprises a frame part 2supporting two rollers 3, 4 around which the endless cross-belt 5 isrunning. One of the rollers 4 is the drive roller 4 connected to a rotor6 by means of a toothed belt 7. The frame part 2 further carries asupport plate 8 supporting the cross-belt 5 on the side opposite to theside forming the article-supporting surface 9 of the cross-belt unit 1.The rotor 6 is situated above two stationary electric stator parts 10.

The schematic view in FIG. 4 of the first embodiment of the cross-beltunit 1 may be compared to a second embodiment of a cross-belt unit 1′shown in FIGS. 5-8. In the second embodiment, the transmission meanscomprises an intermediate roller 11 connected at a first end to therotor 6 by means of a first belt and at a second end thereof to thedrive roller 4 by means of a second belt 7′. This configuration providesa higher freedom of design and of changing and makes variations of agiven design as the path and length of the first belt 7 may be variedeasily. On FIGS. 6, 7 and 8, the stationary linear drive motors 12 andthe stationary track part 13 are indicated.

The cross-belt units 1, 1′ are arranged in a consecutive manner formingan articulated conveyor 14 which preferably forms a closed loop as shownin FIG. 8. FIGS. 7 and 8 are not particularly for the second embodiment,the cross-belt unit 1 of the first embodiment may be arrangedcorrespondingly.

The feed-back system shown in FIGS. 9 a)-d) comprises a rotor 6 mountedin a cross-belt unit 1 as shown in FIG. 9 a), wherein the rotor 6 has aplurality of longitudinal, reflective stripes 15 as shown in FIG. 9 b).The movement of the rotor 6 is measured by a stationary arrangeddetector 16 shown in FIG. 9 c) having a light source 17 and a lightreflection detector 18 producing an output 19 as shown in FIG. 9 d).

Two embodiments of means for providing horizontal alignment of thearticle-supporting unit are shown in FIG. 10. The cross-belt unit 1 runson the stationary track part 13 by means of one wheel 20, 21 at eachside of the track 13. The horizontal alignment is achieved by a spring22 extending along the track 13 near the stationary electric stator part10 and engaging a horizontal wheel 23 of the cross-belt unit 1, biasingthe unit 1 towards the opposite side at which a second horizontal wheel24 of the unit 1 thereby ensuring the correct horizontal position of therotor 6 with respect to the stationary electric stator part 10. A secondembodiments is also shown in FIG. 10 for providing horizontal alignment,in which the horizontal wheel 24 is engaging a two-sided track 25 of thetrack part, thereby ensuring the correct horizontal position of therotor 6 with respect to the stationary electric stator part 10.

FIG. 11 is an embodiment of vertical alignment of the article-supportingunit, wherein the stationary electric stator part 10 is hinged on thetrack part 13 such that is may turn as indicated by the arrow A. Abiasing force, indicated with arrow B is provided by means of a spring26 so that the stator part 10 is moved against the rotor 6 so as toclose the air gap. A wheel 27 is arranged on the stator part 10 toengage the frame part 2 of the cross-belt unit 1 to prevent collisionbetween the rotor 6 and the stator part 10.

The rotor 6 shown in FIGS. 12 a) and b) has an actual aluminium tube 28equipped with a helical rolled steel inner tube 29, which is stretchedprior to insertion into the aluminium tube 28, where after it isreleased and assumes the shape that keeps it resiliently in place insidethe aluminium tube 29.

The rotor 6 shown in FIGS. 13 a) and b) has an actual aluminium tube 28equipped with three rolled shells, together forming the steel tube 29,of which each shell has a diameter exceeding the inner diameter of thealuminium tube 28 and a perimeter length less than the inner perimeterlength of the aluminium tube 28 so that the shells may be deformed, i.e.having the free ends thereof pressed together to decrease the diameter,prior to insertion into the aluminium tube 28, where after they arereleased and assume the shape that keep them resiliently in place insidethe aluminium tube 28.

The rotor shown in FIGS. 14 a) and b) has an actual steel tube 29surrounded with an aluminium sheet forming the outer tube 28, the sheetbeing either rolled into a shape that keeps it resiliently in place ormay be glued or welded together.

The rotor shown in FIGS. 15 a) and b) has an actual aluminium tube 28equipped with an inner steel tube 29 formed by a helical wound quadraticwire that prior to insertion into the aluminium tube 28 is stretched todecrease its outer diameter. After insertion the helical wound wire isreleased and it resumes its shape which keeps it resiliently in placeinside the aluminium tube 28.

A tilt-tray unit 30 according to the second aspect of the invention isshown in FIGS. 16 and 17, and a sorter conveyor 33 having the tilt-trayunits 30 is shown in FIGS. 18 and 19. The tilt-tray unit 30 has atilt-tray 31 defining an article-supporting surface 9 and beingsupported on a tilt unit 32 that supports the tray in upright,article-carrying position as shown as well as in a tilted position toeither of the sides in a manner well-known in the prior art. The tiltingfunction is driven by a rotor 6 via a toothed belt 7 wherein the rotor 6is activated by means of one or more stationary electric stator parts 10arranged along the path of the sorter conveyor as described above.

1. A conveyor comprising a stationary track part, at least onestationary electric stator part that may be activated selectively toproduce a travelling magnetic field and is arranged along the stationarytrack part, a sorter movably arranged to be driven along the stationarytrack part by means of drive means, and a plurality ofarticle-supporting units arranged on the sorter, each unit having aflexible member defining an article-supporting surface and beingarranged movably in a direction substantially perpendicularly to thedirection of motion of the sorter, and a rotor susceptible to saidtravelling magnetic field and arranged to apply a driving force to theflexible member when co-operating with the at least one stationaryelectric stator part, wherein each article-supporting unit comprises adrive roller which over a part of its circumference is in drivingcontact with the flexible member, and a transmission means fortransmitting driving force from the rotor to the drive roller.
 2. Aconveyor according to claim 1, wherein the transmission means has agearing ratio in the range of 1.5 to 5, preferably in the range of 2 to4, between the rotor and the drive roller, so that the rotor has ahigher angular speed than the drive roller.
 3. A conveyor according toclaim 1, wherein the flexible member is an endless belt.
 4. A conveyoraccording to claim 1, and comprising locking means for preventing themotion of the flexible members of the article-supporting units.
 5. Aconveyor according to claim 4, wherein the locking means are activatedby the deviation from alignment of adjacent article-supporting units incurved sections of the stationary track part.
 6. A conveyor according toclaim 4, wherein the locking means are activated by the apparentcentrifugal force on article-supporting units moving in curved sectionsof the stationary track part.
 7. A conveyor according to claim 4,wherein the locking means are released by means of magnetic forces.
 8. Aconveyor according to claim 4, wherein the locking means are released bymeans of the attraction forces between the at least one stationaryelectric stator part and the rotor.
 9. A conveyor according to claim 4,wherein the locking means comprises on each article-supporting unit astationary part in engagement with a movable part moving simultaneouslywith the flexible member, characterised in that the resistance againstmutual movements between the stationary part and the movable part issubstantially lowered during mutual movement between said two parts. 10.A conveyor according to claim 9, wherein the stationary part is asupport surface supporting the side of the flexible member opposite thearticle-supporting surface, and the friction characteristics between theflexible member and the support surface are characterised in that thefriction is substantially lowered at mutual movement between said twoparts.
 11. A conveyor according to claim 1, comprising tilting means fortilting the article-supporting surfaces inwardly when passing curvedsections of the stationary track part, and drive mans for driving saidtilting means, wherein said drive means are driven by the deviation fromalignment of adjacent article-supporting units in curved sections of thestationary track part.
 12. A conveyor according to claim 1 comprisingfeedback means for providing an output to a control unit of the conveyorindicative of the movement of the flexible member.
 13. A conveyoraccording to claim 12, wherein the feedback means comprise a camera fordetecting at least two consecutive images of at least one of theflexible member, the rotor or the transmission, and computing means forproviding an output from said images.
 14. A conveyor according to claim12, wherein the feedback means detect the extend of rotation of therotor of each of the article-supporting units and provide an outputaccordingly.
 15. A conveyor according to claim 14, wherein the rotorcomprises at least one irregularity of the susceptibility to thetravelling magnetic filed, causing the power supplied to the stationaryelectric stator to vary when the at least one irregularity passes thestationary electric stator during rotation of the rotor, said variationbeing detected by the feedback means.
 16. A conveyor according to claim14, wherein the outer surface of the rotor comprises at least oneirregularity of its optical characteristics and the feedback meanscomprises a detector for detecting the variation of reflection of alight source caused by the at least one irregularity during rotation ofthe rotor and providing an output accordingly.
 17. A conveyor accordingto claim 12, wherein each article-supporting unit comprises signal meansfor producing a signal indicative of the movement of the flexible memberand the feedback means comprises a detector for detecting said signalsand producing an output accordingly.
 18. A conveyor according to claim17, wherein the signal means comprises at least one passive circuitmoving simultaneously with the flexible member, the passive circuitshaving an induction part for inducting an electric current when exposedto a magnetic field and a transmitter part for transmitting anelectromagnetic signal and driven by the inducted current, the feedbackmeans comprising a detector for detecting said signal and providing anoutput according to the variations of the signal due to said movement ofthe one or more passive circuits.
 19. A conveyor according to claim 1,comprising horizontal alignment means for situating thearticle-supporting units precisely with respect to the at least onestationary electric stator part in the direction transversely to theconveyance direction of the conveyor.
 20. A conveyor according to claim19, wherein the horizontal alignment means comprises a horizontal wheelarranged on the article-supporting unit and a corresponding two-sidedtrack arranged on the stationary track part.
 21. A conveyor according toclaim 19, wherein the horizontal alignment means comprises biasing meansfor providing a biasing force to the article-supporting units toward oneside in the transversal direction and reaction means for producing acounter reaction force against said biasing force.
 22. A conveyoraccording to claim 21, wherein the biasing means comprises at least onepermanent magnet arranged on each of the article-supporting units and amagnetic susceptible stationary part arranged near the at least onestationary electric stator part displaced in the transversal directionwith respect to said at least one permanent magnet such that the mutualmagnetic force between the at least one permanent magnet and saidstationary part constitutes said biasing force.
 23. A conveyor accordingto claim 1, wherein the at least one stationary electric stator part issuspended movably and comprises biasing means for biasing the statorpart towards the rotors of the article-supporting units and one or moredistance means for providing a suitable distance between the stator partand the rotors.
 24. A conveyor according to claim 1, wherein said drivemeans comprises one or more stationary linear motor stator partsinteracting with said rotors to produce a driving force to drive thesorter along the stationary track part.
 25. A conveyor comprising astationary track part, at least one stationary electric stator part thatmay be activated selectively to produce a travelling magnetic field andis arranged along the stationary track part, a sorter movably arrangedto be driven along the stationary track part by means of drive means,and a plurality of article-supporting units arranged on the sorter, eachunit having a tray defining an article-supporting surface and beingarranged to be tilted in a direction substantially perpendicularly tothe direction of motion of the sorter, and a rotor susceptible to saidtravelling magnetic field and arranged to apply a driving force to tiltthe tray when co-operating with the at least one stationary electricstator part.
 26. A conveyor according to claim 25 comprising feedbackmeans for providing an output to a control unit of the conveyorindicative of the movement of the trays.
 27. A conveyor according toclaim 26, wherein the feedback means comprise a camera for detecting atleast two consecutive images of at least one of the tray, the rotor or atransmission there between, and computing means for providing an outputfrom said images.
 28. A conveyor according to claim 26, wherein thefeedback means detect the extend of rotation of the rotor of each of thearticle-supporting units and provide an output accordingly.
 29. Aconveyor according to claim 28, wherein the rotor comprises at least oneirregularity of the susceptibility to the travelling magnetic filed,causing the power supplied to the stationary electric stator to varywhen the at least one irregularity passes the stationary electric statorduring rotation of the rotor, said variation being detected by thefeedback means.
 30. A conveyor according to claim 28, wherein the outersurface of the rotor comprises at least one irregularity of its opticalcharacteristics and the feedback means comprises a detector fordetecting the variation of reflection of a light source caused by the atleast one irregularity during rotation of the rotor and providing anoutput accordingly.
 31. A conveyor according to claim 26, wherein eacharticle-supporting unit comprises signal means for producing a signalindicative of the movement of the tray and the feedback means comprisesa detector for detecting said signals and producing an outputaccordingly.
 32. A conveyor according to claim 21, wherein the signalmeans comprises at least one passive circuit moving simultaneously withthe tray, the passive circuits having an induction part for inducting anelectric current when exposed to a magnetic field and a transmitter partfor transmitting an electromagnetic signal and driven by the inductedcurrent, the feedback means comprising a detector for detecting saidsignal and providing an output according to the variations of the signaldue to said movement of the one or more passive circuits.
 33. A conveyoraccording to claim 25, comprising horizontal alignment means forsituating the article-supporting units precisely with respect to the atleast one stationary electric stator part in the direction transverselyto the conveyance direction of the conveyor.
 34. A conveyor according toclaim 33, wherein the horizontal alignment means comprises a horizontalwheel arranged on the article-supporting unit and a correspondingtwo-sided track arranged on the stationary track part.
 35. A conveyoraccording to claim 33, wherein the horizontal alignment means comprisesbiasing means for providing a biasing force to the article-supportingunits toward one side in the transversal direction and reaction meansfor producing a counter reaction force against said biasing force.
 36. Aconveyor according to claim 35, wherein the biasing means comprises atleast one permanent magnet arranged on each of the article-supportingunits and a magnetic susceptible stationary part arranged near the atleast one stationary electric stator part displaced in the transversaldirection with respect to said at least one permanent magnet such thatthe mutual magnetic force between the at least one permanent magnet andsaid stationary part constitutes said biasing force.
 37. A conveyoraccording to claim 25, wherein the at least one stationary electricstator part is suspended movably and comprises biasing means for biasingthe stator part towards the rotors of the article-supporting units andone or more distance means for providing a suitable distance between thestator part and the rotors.
 38. A conveyor according to claim 25,wherein said drive means comprises one or more stationary linear motorstator parts interacting with said rotors to produce a driving force todrive the sorter along the stationary track part.
 39. A conveyorcomprising a stationary track part, at least one stationary electricstator part that may be activated selectively to produce a travellingmagnetic field and is arranged along the stationary track part, a sortermovably arranged to be driven along the stationary track part by meansof drive means, and a plurality of article-supporting units arranged onthe sorter, each unit having article-supporting means defining anarticle-supporting surface and having discharge means to dischargearticles therefrom in a direction substantially perpendicularly to thedirection of motion of the sorter, and a rotor susceptible to saidtravelling magnetic field and arranged to apply a driving force to thedischarge means when co-operating with the at least one stationaryelectric stator part, wherein said drive means comprises one or morestationary linear motor stator parts interacting with said rotors toproduce a driving force to drive the sorter along the stationary trackpart.
 40. A conveyor according to claim 1, wherein the rotors of atleast one of the article-supporting units is a tubular rotor for anasynchronous motor comprising an inner tubular magnetic conductingmember and an outer tubular member being electric conducting andnon-magnetic conducting, wherein a first of said tubular members is atube and the second of said tubular members consist of a length ofmaterial being deformed into a tubular shape fastened to the firsttubular member so as to preserve the tubular shape of the second tubularmember as well as the contact between the two tubular members.
 41. Aconveyor according to claim 25, wherein the rotors of at least one ofthe article-supporting units is a tubular rotor for an asynchronousmotor comprising an inner tubular magnetic conducting member and anouter tubular member being electric conducting and non-magneticconducting, wherein a first of said tubular members is a tube and thesecond of said tubular members consist of a length of material beingdeformed into a tubular shape fastened to the first tubular member so asto preserve the tubular shape of the second tubular member as well asthe contact between the two tubular members.
 42. A conveyor according toclaim 39, wherein the rotors of at least one of the article-supportingunits is a tubular rotor for an asynchronous motor comprising an innertubular magnetic conducting member and an outer tubular member beingelectric conducting and non-magnetic conducting, wherein a first of saidtubular members is a tube and the second of said tubular members consistof a length of material being deformed into a tubular shape fastened tothe first tubular member so as to preserve the tubular shape of thesecond tubular member as well as the contact between the two tubularmembers.